1. Field of the Invention
The present invention relates to a cooling device that is provided with a heat sink (hereinbelow referred to as a heat sink-type cooling device), and in particular, to a heat sink-type cooling device that employs a liquid cooling technique to improve cooling efficiency.
2. Description of the Related Art
In vehicles such as electric vehicles and fuel cell powered vehicles which employ an alternating current motor as a power source, semiconductor components such as switching elements (e.g., IGBT (Insulated Gate Bipolar Transistor)) and DC/DC converters are mounted in a power converter in order to convert a direct current supplied from a battery into an alternating current. In such a power converter, the amount of heat generated by the switching elements is significantly large and is increasing as the size of power converters increases year by year; therefore it is necessary to cool down the power converter more efficiently.
A structure for cooling down power converters is disclosed, for example, in Japanese Unexamined Patent Application, First Publication No. Hei 9-19163. According to the structure, the power converter is provided with a heat sink in which electronic semiconductor components are placed on the flat top surface, and a number of cooling grooves are formed on the bottom surface to which a base is fixed, and with a cooling groove section which supplies cooling water to a space enclosed by the base and the bottom surface of the heat sink to circulate the cooling water. The cooling groove section comprises the cooling grooves and a number of thin fins that is used for heat exchange in which the cooling water flows through spaces formed by adjoining fins.
The above-described structure makes it possible to enhance the amount of heat dissipated by means of the fins, so that it is advantageous in that a heat sink-type cooling device having high cooling capacity can be achieved. However, since the flow of the cooling water flowing along the fins flows laminarly in the spaces formed by adjoining fins, only cooling water flowing near the fins contributes to heat exchange. Accordingly, the amount of heat dissipated by means of the fins will eventually reach an upper limit, and hence it is impossible to obtain an expected cooling capacity. Although it is possible to enhance the amount of heat dissipated by expanding the area of the fins, a problem will arise in that the height of the heat sink increases and the size of the heat sink increases.
It is therefore an object of the present invention to provide a heat sink-type cooling device which has high cooling capacity with a miniaturized structure, and which can enhance the amount of heat dissipated without increasing the size of the fins.
In order to achieve the above object, a heat sink-type cooling device according to the present invention comprises: a heat sink (for example, a heat sink 5 in the embodiment) which is provided with a passage (a passage 6 in the embodiment) through which coolant flows, and a plurality of fin groups (for example, fin groups 21 in the embodiment) which are provided in the passage and each of which is comprised of a plurality of fins (for example, fins 22 in the embodiment) that are disposed in parallel with the direction of the coolant flow and are aligned in the thickness direction of the fins, wherein the heat sink removes heat from a heat source (for example, electronic devices 8 in the embodiment) which contacts with a surface (for example, an upper surface 7 in the embodiment) of the heat sink, and a fin of a fin group and another fin of another fin group adjoining to the fin group in the direction of the flow are arranged at a distance in the thickness direction of the fins. With such a structure, when the coolant flows from a fin group to another fin group, the coolant flow becomes turbulent due to the structure in which the adjoining fin groups are placed at a distance, so that it is possible to remove greater amounts of heat from the heat source through the fins. Consequently, the cooling capacity can be enhanced as compared with that in conventional cooling devices.
In the present invention, it is preferable that one of the surfaces be provided with a heat source arrangement portion (for example, apparatus arrangement portions 26 in the embodiment) for arranging the heat source at the position closest to the fin groups. With such a structure, in addition to the above-described effect, it is possible to arrange the heat source at the positions closest to the fin groups on the surface where the heat source can be placed. For this reason, it is possible to efficiently remove heat from the heat source that should be further cooled in preference to other devices.
In the present invention, it is preferable that the fin group and another fin group adjoining the fin group in the direction of the flow be closely arranged. With such a structure, in addition to the above-described effect, it is possible to enhance an effect obtained by the turbulent flow, which is generated by an arrangement in which the fin groups are arranged at a distance, to the maximum extent. For this reason, it is possible to further enhance the capacity to remove heat.
In the present invention, it is preferable that the fin groups be arranged in a manner such that coolant flow from two adjoining spaces formed by three adjoining fins of the upstream fin group joins at a space between adjoining fins of the downstream fin group to make the coolant flow turbulent. It is also preferable that the fin groups be arranged in a manner such that the coolant flowing near the surfaces of the fins of an upstream fin group flows at portions distant from the surfaces of the fins of a downstream fin group adjoining the upstream fin group in the direction of the flow, and a part of the coolant flowing at the spaces between the fins of the upstream fin group flows near the surfaces of the fins of the downstream fin group. With such structures, it is possible to efficiently remove heat from the fins.
In the present invention, it is preferable that the pitch of the fin be made as narrow as possible and the thickness of the fin be made as thick as possible without blocking the flow. With such a structure, it is possible to lower the temperature of the heat source to the maximum extent.